A high-strength and high-plasticity synergistic multi-principal element high-entropy alloy and preparation method thereof

Abstract

The present invention discloses a high-strength and high-plasticity synergistic multi-principal element high-entropy alloy and a preparation method thereof. By atomic percentage, it includes 27-31% of Ni, 27-31% of Co, 27-31% of Cr, 10-12% of Al, and 1-3% of Ta. The multi-principal element high-entropy alloy has a duplex structure of FCC matrix phase and micron-scale B2 phase. Through simple homogenization, key warm rolling, and subsequent annealing recrystallization, the "strength-plasticity" mutual exclusion phenomenon of metal materials can be broken. When the strength of the as-cast NiCoCr-based high-entropy alloy remains at the original level, its plasticity is nearly doubled, greatly improving the comprehensive mechanical properties of the material. The composition fluctuation effect enables the stacking fault energy and lattice strain to change spatially at the nanoscale, resulting in the change of dislocation resistance in the nanospace, significantly promoting the storage, multiplication, cross-slip ability, and interaction of dislocations, thereby improving the work hardening ability and plasticity.

Description

Technical Field

[0001] The present invention relates to the field of alloy material preparation technology, and in particular to a high-strength and plasticity synergistic multi-principal element high-entropy alloy and a preparation method thereof. Background Art

[0002] The rapid development of modern industry and technology has led to an increasingly urgent demand for high-performance metal structural materials. Therefore, researchers have tried to use a variety of strengthening and toughening strategies to improve the comprehensive mechanical properties of materials, such as solid solution strengthening, grain boundary strengthening, second phase strengthening, and dislocation strengthening. However, the commonly used strengthening and toughening strategies lead to the "strength-plasticity" mutual exclusion phenomenon that is prevalent in metal structural materials, that is, when the strength increases, the plasticity decreases, or when the plasticity increases, the strength decreases. Therefore, how to break this "strength-plasticity" mutual exclusion phenomenon of metal structural materials to improve the synergy of strength and plasticity is a goal that researchers in this field are constantly pursuing, and it has important engineering and scientific value.

[0003] Multi-principal high-entropy alloys are a new type of high-performance metal material with broad application potential. HEAs break the design concept of a single principal element in traditional alloys and create new ideas for alloy design. Among the many HEAs systems currently available, face-centered (FCC) H / MEAs are the most popular, such as FeCoCrNiMn, FeCoCrNi and NiCoCr, which generally have low stacking fault energy. Studies have shown that they have very low stacking fault energy, short-range ordered structures at the atomic scale, and high twin formation ability, and exhibit multi-stage deformation mechanism characteristics, including dislocation plane slip, twinning, and even phase transformation to improve the work hardening ability of the material. However, it still has the "strength-plasticity" mutual exclusion phenomenon similar to that in traditional metal materials, which limits its engineering application. Therefore, improving the synergy of strength and plasticity in multi-principal high-entropy alloys is a key scientific issue that needs to be solved urgently. Summary of the invention

[0004] In order to solve the problem of how to improve the synergy between strength and plasticity of metal structural materials, the present invention provides a high-strength-plasticity synergistic multi-principal-component high-entropy alloy and a preparation method. By adopting homogenization and warm rolling and subsequent annealing and recrystallization, the "strength-plasticity" mutual exclusion phenomenon of metal materials can be broken, the mechanical properties of the materials can be greatly improved, and their high performance can be achieved.

[0005] The present invention is achieved through the following technical solutions:

[0006] A high-strength and plasticity synergistic multi-principal element high-entropy alloy comprises, by atomic percentage, 27-31% Ni, 27-31% Co, 27-31% Cr, 10-12% Al and 1-3% Ta.

[0007] Preferably, the multi-principal component high entropy alloy has a dual-phase structure, including an FCC matrix phase and a micron-scale B2 phase.

[0008] Preferably, the tensile strength σ of the multi-principal element high-entropy alloy UTS is 1100-1160 MPa, the yield strength σ y is 660-680 MPa, and the fracture elongation rate is greater than 35%.

[0009] A preparation method of a high-strength and high-plasticity synergistic multi-principal element high-entropy alloy comprises the following steps:

[0010] Step 1: Mix various metal raw materials to prepare an alloy ingot;

[0011] Step 2: Perform homogenization treatment on the alloy ingot obtained by melting in Step 1;

[0012] Step 3: Perform multi-pass warm rolling treatment on the alloy homogenized in Step 2;

[0013] Step 4: Anneal and recrystallize the alloy obtained by warm rolling to obtain a multi-principal element high-entropy alloy strong.

[0014] Preferably, in Step 1, an alloy ingot is prepared by a melting process, and the process is as follows:

[0015] The alloy is melted by a vacuum arc melting method. During the melting process, first evacuate to 2 Pa, then introduce high-purity argon gas and evacuate again, and repeat the furnace washing process multiple times. The melting induction current is 500-550 A. During the alloy melting process, electromagnetic stirring is accompanied, and after repeated remelting, it is cooled in a water-cooled copper crucible to obtain an ingot.

[0016] Preferably, the temperature of the homogenization treatment in Step 2 is 1210-1250 °C.

[0017] Preferably, the warm rolling temperature in Step 3 is 450-550 °C, and the total deformation amount is 65-75%.

[0018] Preferably, the annealing time in Step 4 is 3-5 min.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] The present invention provides a high-strength and high-plasticity synergistic multi-principal element high-entropy alloy. For multi-principal element high-entropy alloys, through simple homogenization and key warm rolling and subsequent annealing recrystallization, the "strength-plasticity" mutual exclusion phenomenon of metal materials can be broken. Combining the multi-principal element characteristics of high-entropy alloys and the relatively high tendency of "chemical short-range order", the high-entropy alloys processed by this technology can generate "deformation-induced compositional fluctuations" during deformation. The compositional fluctuation effect enables the stacking fault energy and lattice strain to vary spatially at the nanoscale, resulting in the dislocation resistance also changing in the nanospace, significantly promoting the storage, multiplication, cross-slip ability, and interaction of dislocations, thereby improving the work-hardening ability and plasticity. The formation of dislocation cells is conducive to the capture, multiplication, and storage of dislocations, so it can improve the work-hardening ability of the material and further promote the uniform deformation ability. In addition, dislocation cells may become dislocation sources and improve the plasticity of the material. The method provided by the present invention doubles the plasticity of the material while maintaining its original strength level. The plasticity of the as-cast NiCoCr-based high-entropy alloy is increased from 21% to 39%, showing good room-temperature mechanical properties. Based on the above characteristics, it is possible to extend the method provided by the present invention to other high-entropy alloy material systems to prepare metal structural materials with excellent strength-plasticity synergy, which is of great engineering and scientific significance.

[0021] The preparation method provided by the present invention is simple. More excellent mechanical properties can be obtained by simply homogenizing the as-cast high-entropy alloy, followed by warm rolling and recrystallization. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Microstructures of the NiCoCr-based high-entropy alloy of the present invention after cold rolling (CR) and warm rolling followed by recrystallization annealing;

[0023] Figure 2 Comparison chart of tensile properties of the NiCoCr-based high-entropy alloy of the present invention under different processes;

[0024] Figure 3 Microstructures of the NiCoCr-based high-entropy alloy of the present invention after tensile deformation of cold-rolled and warm-rolled samples;

[0025] Figure 4 Microstructures of the NiCoCr-based high-entropy alloy of the present invention before and after tensile deformation of warm-rolled samples. DETAILED DESCRIPTION OF THE INVENTION

[0026] The following further elaborates on the present invention in detail with reference to the accompanying drawings. The following is an explanation rather than a limitation of the present invention.

[0027] A high-strength and high-plasticity synergistic multi-principal element high-entropy alloy, by atomic percentage (at.%), includes 27 - 31% of Ni, 27 - 31% of Co, 27 - 31% of Cr, 10 - 12% of Al, and 1 - 3% of Ta;

[0028] The above raw materials are high-purity metal particles with a purity of not less than 99.9%.

[0029] The NiCoCr-based high-entropy alloy has a "FCC + B2" duplex structure, and the tensile strength σ UTS of the alloy is 1100 - 1160 MPa, the yield strength σ y is 660 - 680 MPa, and the elongation at fracture is greater than 35%.

[0030] The preparation method of the above high-strength and high-plasticity synergistic multi-principal-element high-entropy alloy includes the following steps:

[0031] Step 1: Mix metal particles of 27 - 31% Ni, 27 - 31% Co, 27 - 31% Cr, 10 - 12% Al, and 1 - 3% Ta evenly by atomic percentage.

[0032] When weighing the raw materials, the weight is accurate to 0.01 g, and then the alloy is melted by vacuum arc melting method.

[0033] During the melting process, first evacuate to 2 Pa, then introduce high-purity argon and evacuate again, repeat the furnace washing three times to ensure a high-purity vacuum environment, the melting induction current is 500 - 550 A, the alloy is accompanied by electromagnetic stirring during the melting process, and remelt 5 times repeatedly to ensure the compositional uniformity, and finally cool in a water-cooled copper crucible to obtain an ingot;

[0034] Step 2: Homogenize the alloy ingot obtained by melting in Step 1 at a temperature of 1210 - 1250 °C;

[0035] Step 3: Perform multi-pass warm rolling on the alloy ingot homogenized in Step 2, the warm rolling temperature is 450 - 550 °C, and the total deformation is controlled at 65 - 75%;

[0036] Step 4: Perform annealing and recrystallization treatment on the alloy ingot obtained by warm rolling, the annealing temperature is 1100 - 1150 °C, and the time is 3 - 5 min to obtain the multi-principal-element high-entropy alloy.

[0037] The preparation method of the above high-strength and high-plasticity synergistic multi-principal-element high-entropy alloy is conducive to the synergistic toughening of "deformation-induced compositional fluctuations" and dislocation cell structures. By preparing a NiCoCr-based high-entropy alloy, through homogenization, key warm rolling and subsequent recrystallization annealing, a high-entropy alloy with a duplex "FCC+B2" structure is obtained. Combining the multi-principal-element characteristics of the high-entropy alloy and the relatively high tendency of "chemical short-range order", the high-entropy alloy treated by this process can generate "deformation-induced compositional fluctuations" during deformation, and the local compositional fluctuations will affect the distribution of stacking fault energy and lattice strain in the nanoscale space of the material. Therefore, the dislocation resistance also changes in the nanoscale space. In this case, the movement rate of dislocations is significantly reduced, promoting their interaction, interlocking and accumulation, significantly promoting the multiplication, storage and cross-slip ability of dislocations, further causing the formation of dislocation cells, and this continuous process will continuously improve the work-hardening ability and uniform deformation ability of the material.

[0038] Example 1

[0039] A preparation method of a high-strength and high-plasticity synergistic multi-principal-element high-entropy alloy includes the following steps:

[0040] Step 1: Mix metal particles of 31% Ni, 27% Co, 29% Cr, 11% Al and 2% Ta evenly by atomic percentage.

[0041] During the melting process, first evacuate to 2 Pa and then introduce high-purity argon and then evacuate again, repeat the furnace washing three times to ensure a high-vacuum environment. The melting induction current is 550 A. The alloy is accompanied by electromagnetic stirring during the melting process and remelted 5 times repeatedly to ensure compositional uniformity. Finally, it is cooled in a water-cooled copper crucible to obtain an alloy ingot;

[0042] Step 2: Homogenize the alloy ingot obtained in Step 1 at 1225 °C;

[0043] Step 3: Warm roll the alloy ingot homogenized in Step 2 at 500 °C, and control the total deformation amount at 70%;

[0044] Step 4: Recrystallize and anneal the alloy ingot after warm rolling in Step 3 at 1150 °C for 3 min to obtain a multi-principal-element high-entropy alloy.

[0045] This multi-principal-element high-entropy alloy is a duplex FCC+B2 alloy with excellent strength-plasticity matching. According to the requirements of the GB / T228.1-2010 standard, the mechanical properties of the alloy are measured as Figure 2 shown by the WR curve in: the tensile strength σ UTS is 1155 MPa, the yield strength σ y is 678 MPa, and the fracture elongation ε TIt is 38%. The alloy has excellent strength-ductility synergy and work hardening ability. The TEM results show that significant "composition fluctuations" and dislocation cells are generated in the deformed microstructure, as shown in Figure 3 (b) and 4(a).

[0046] Example 2

[0047] A preparation method of a high-strength and high-ductility synergistic multi-principal element high-entropy alloy, comprising the following steps:

[0048] Step 1: Mix evenly metal particles of 27% Ni, 29% Co, 31% Cr, 10% Al, and 3.0% Ta by atomic percentage.

[0049] During the melting process, first evacuate to 2 Pa, then introduce high-purity argon and evacuate again, repeat the furnace washing three times to ensure a high-vacuum environment. The melting induction current is 525 A. During the alloy melting process, electromagnetic stirring is accompanied, and remelting is repeated 5 times to ensure composition uniformity. Finally, cool in a water-cooled copper crucible to obtain an alloy ingot;

[0050] Step 2: Homogenize the alloy ingot obtained in Step 1 at 1210 °C;

[0051] Step 3: Warm-roll the homogenized alloy ingot obtained in Step 2 at 550 °C, and control the total deformation amount at 75%;

[0052] Step 4: Recrystallize and anneal the warm-rolled alloy ingot obtained in Step 3 at 1100 °C for 5 min to obtain a multi-principal element high-entropy alloy.

[0053] This multi-principal element high-entropy alloy is a dual-phase FCC + B2 alloy with excellent strength-ductility matching. According to the requirements of the GB / T228.1-2010 standard, the measured tensile strength σ UTS is 1135 MPa, the yield strength σ y is 669 MPa, and the fracture elongation ε T is 40%. The alloy has excellent strength-ductility synergy.

[0054] Example 3

[0055] A preparation method of a high-strength and high-ductility synergistic multi-principal element high-entropy alloy, comprising the following steps:

[0056] Step 1: Mix evenly metal particles of 29% Ni, 31% Co, 22% Cr, 12% Al, and 1% Ta by atomic percentage.

[0057] During the melting process, first evacuate to 2 Pa under vacuum, then introduce high-purity argon gas, and then evacuate again. Repeat the furnace washing three times to ensure a high-vacuum environment. The melting induction current is 550 A. During the alloy melting process, electromagnetic stirring is carried out, and remelting is repeated 5 times to ensure the uniformity of the composition. Finally, cool in a water-cooled copper crucible to obtain an alloy ingot;

[0058] Step 2: Homogenize the alloy ingot obtained in Step 1 at 1250 °C;

[0059] Step 3: Warm-roll the alloy ingot homogenized in Step 2 at 450 °C, and control the total deformation amount within 65%;

[0060] Step 4: Carry out recrystallization annealing on the alloy ingot warm-rolled in Step 3 at 1130 °C for 4 min to obtain a multi-principal element high-entropy alloy.

[0061] This multi-principal element high-entropy alloy is a dual-phase FCC + B2 alloy with excellent strength-ductility matching. According to the requirements of the GB / T228.1-2010 standard, the measured tensile strength σ UTS is 1160 MPa, the yield strength σ y is 660 MPa, and the fracture elongation ε T is 37%. The alloy has excellent strength-ductility synergy.

[0062] Comparative Example 1

[0063] A NiCoCr-based high-entropy alloy with the same composition as that in Example 1 is obtained by the same arc melting process, and the mechanical properties of the material are tested. According to the requirements of the GB / T228.1-2010 standard, the measured mechanical properties of the as-cast alloy are as shown by the curve As-cast in Figure 2 : the tensile strength σ UTS is 1061 MPa, the yield strength σ y is 689 MPa, and the fracture elongation εT is 21%. The strength of the as-cast alloy is comparable to that of Example 1, but the plasticity is only about 50% of that of Example 1.

[0064] Comparative Example 2

[0065] The alloy composition in this Comparative Example 2 is the same as that in Example 1, and the preparation method is basically the same. The difference lies in the rolling temperature in Step 3, which is specifically as follows:

[0066] In Step 3 of this Comparative Example 2, the homogenized alloy ingot is cold-rolled at room temperature, the temperature is 25 °C, and the total deformation amount is controlled within 75%. The mechanical properties of the obtained alloy material are tested. According to the requirements of the GB / T228.1-2010 standard, the measured mechanical properties of the alloy are as shown by the curve CR in Figure 2 : the tensile strength σ UTS is 703 MPa, the yield strength σy is 1154 MPa, and the fracture elongation ε T is 20%. Its strength and plasticity are basically the same as those of the as-cast material, and the plasticity is only about 50% of that in the example. The TEM results show that there are no "composition fluctuations" and dislocation cell results similar to those in the example in the deformed structure, as shown in Figure 3 (a) and 4(b).

[0067] Comparative Example 3

[0068] The alloy composition in this Comparative Example 3 is the same as that in Example 1, and the preparation methods are basically the same. The differences lie in the preparation processes of Step 3 and Step 4, which are specifically as follows:

[0069] Change the warm rolling in Step 3 and the annealing recrystallization step in Step 4 to hot rolling of the homogenized alloy ingot at 1200 °C with a deformation amount of 75%, and conduct mechanical property tests on the hot-rolled alloy material. According to the requirements of the GB / T 228.1-2010 standard, the measured mechanical properties of the alloy are as shown in Figure 2 the curve HR in: the tensile strength σ UTS is 1378 MPa, and the yield strength σ y is 1010 MPa, and the fracture elongation ε T is 13%. Although the strength is significantly improved compared with the as-cast material, the plasticity is significantly decreased, and the "strength-plasticity" mutual exclusion phenomenon still appears.

[0070] Figure 1 This is the microstructure of the NiCoCr-based high-entropy alloy of the present invention after warm rolling and then recrystallization annealing, and the microstructure of the cold rolling and then recrystallization annealing in the representative Comparative Example 2. It can be seen that there is no significant difference in the initial microstructure, and both have the "FCC + B2" structure;

[0071] Figure 2 This is the tensile property comparison diagram of the NiCoCr-based high-entropy alloy of the present invention in the example and the representative comparative example. It can be seen that the WR curve has the most excellent strength-plasticity synergy and more excellent work-hardening ability;

[0072] Figure 3 This is the microstructure of the NiCoCr-based high-entropy alloy of the present invention after tensile deformation of the warm rolling sample and the cold rolling sample in the representative Comparative Example 2. It can be seen that a significant dislocation cell structure is formed in the WR sample of the example, while the dislocations are evenly distributed in the CR.

[0073] Figure 4 This is the element distribution diagram of the NiCoCr-based high-entropy alloy of the present invention before and after tensile deformation of the warm rolling sample. It can be seen that there is segregation at the dislocation cell walls after deformation ( Figure 4 (a)), while there is no element segregation before deformation ( Figure 4(b)) This phenomenon indicates that the warm-rolled samples have the "deformation-induced compositional fluctuation" phenomenon during the tensile process.

[0074] The present invention provides a multi-principal element high-entropy alloy, and at the same time provides a new toughening mechanism, that is, the synergistic toughening of "deformation-induced compositional fluctuation" and dislocation cell structure effect. (1) Compositional fluctuation effect: This spatial compositional fluctuation causes the dislocation resistance to change spatially at the nanoscale, so the movement of dislocations is significantly affected. In this case, the movement of dislocations becomes slow, promoting their interaction, interlocking and accumulation, significantly promoting the storage, multiplication and cross-slip ability of dislocations, thus improving the work-hardening ability and ultimately improving the plasticity of the material. (2) Dislocation cell effect: Due to the change of dislocation resistance in the nano-space caused by compositional fluctuation, the positions with high dislocation resistance in the material will be more likely to capture dislocations and form dislocation cell structures during the deformation process. Dislocation cells are a relatively stable dislocation configuration, and the dislocation cell walls will promote the formation of Lomer dislocation locks. The dislocation pinning effect on the cell walls strengthened by immobile Lomer dislocation locks is very strong, so that after the dislocations are depinned, they will quickly pass through the cell interior. The moving dislocations will be terminated and stored on the cell walls without propagating to adjacent dislocation cells. This process is more conducive to the capture, multiplication and storage of dislocations, so it can improve the work-hardening ability of the material and then promote the uniform deformation ability; in addition, when the local stress is large, the dislocation cell structure is more stable and may become a dislocation source to improve the plasticity of the material. In the present invention, for the multi-principal element high-entropy alloy, through simple homogenization, key warm rolling and subsequent annealing recrystallization, the "strength-plasticity" mutual exclusion phenomenon of metal materials can be broken, so that the plasticity of the as-cast NiCoCr-based high-entropy alloy is nearly doubled while its strength remains at the original level. The preparation method provided by the present invention can greatly improve the comprehensive mechanical properties of the material. Based on the above characteristics, it is possible to extend the method provided by the present invention to other high-entropy alloy material systems to prepare metal structural materials with excellent strength-ductility synergy, which is of great engineering and scientific significance.

[0075] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A high-strength and high-plasticity synergistic multi-principal-element high-entropy alloy, characterized in that, by atomic percentage, it includes 27-31% of Ni, 27-31% of Co, 27-31% of Cr, 10-12% of Al and 1-3% of Ta; The preparation method of the high-strength and high-plasticity synergistic multi-principal-element high-entropy alloy includes the following steps: Step 1, mixing various metal raw materials to prepare an alloy ingot; Step 2, performing homogenization treatment on the alloy ingot obtained by melting in Step 1; The temperature of the homogenization treatment is 1210-1250 °C; Step 3, performing multi-pass warm rolling treatment on the alloy homogenized in Step 2; The warm rolling temperature is 450-550 °C, and the total deformation amount is 65-75%; Step 4, annealing and recrystallizing the alloy obtained by warm rolling to obtain a multi-principal-element high-entropy alloy; The annealing temperature is 1100-1150 °C, and the annealing time is 3-5 min.

2. The high-strength and high-plasticity synergistic multi-principal-element high-entropy alloy according to claim 1, characterized in that, In Step 1, an alloy ingot is prepared by a melting process, and the process is as follows: The alloy is melted by a vacuum arc melting method. During the melting process, first evacuate to 2 Pa, then introduce high-purity argon gas and then evacuate again, and repeat the furnace washing process multiple times. The melting induction current is 500-550 A. During the alloy melting process, electromagnetic stirring is carried out. After repeated remelting, it is cooled in a water-cooled copper crucible to obtain an ingot.

3. The high-strength and high-plasticity synergistic multi-principal-element high-entropy alloy according to claim 1, characterized in that, This multi-principal-element high-entropy alloy has a duplex structure, including an FCC matrix phase and a micron-scale B2 phase.

4. The high-strength and high-plasticity synergistic multi-principal-element high-entropy alloy according to claim 1, characterized in that, The tensile strength of the multi-principal element high-entropy alloy σ UTS is 1100 - 1160 MPa, and the yield strength σ y is 660 - 680 MPa, and the elongation at break is greater than 35%.

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